The days when you could easilly hop your car up are gone. usually the easy things that one could do to an engine worked because the design of the engine was poor to begin with. For instance, putting a split manifold on a 6-cylinder Chevy. Today's engines will not respond well to home-grown attempts at gaining horsepower. Most people can make more noise, not more power.

New filters and a tune up can do wonders. Make sure your kick-down cable is working properly, if it is not, performance in situations requiring power can really be sluggish. A new cable helped out '88 745 GLE a LOT.
--
2 8s & 2 7s 633,000 miles total